Coffee infusion apparatus and method

ABSTRACT

A coffee infusor consisting of a self-contained appliance providing for filtering water to purify and condition it before or after heating, heating it in a closed container to generate pressure to move it, controlled communication from the closed heating chamber to a coffee infusion chamber for timed infusion, where the heated water is contacted with coffee grounds and passed from the infusion chamber to a receptacle to collect the finished coffee infusion.

O United States Patent 1 1 1111 3,793,933

Weber Feb. 26, 1974 COFFEE INFUSION APPARATUS AND 2,615,384 10/1952 Ranz99/282 METHOD 1 3,423,209 1/1969 Weber 99/71 [76] Inventor: Robert L.Weber, 49 Clapboard Rd., New Canaan, Conn, 06340 i ary Exammer Robert W.Jenkms Attorney, Agent, or Firm-Cooper, Dunham, Clark, NOV. 19, Griffin& Moran [21] Appl. No.: 200,300

- [57] ABSTRACT g 229? A coffee infusor consisting of a self-containedPPlin H; J 'ance providing for filtering water to p fy and condi Fieldof Search 99/280 tion it before or after heating, heating it in a closed99/292 307 container to generate pressure to move it, controlled 56 R fcommunication from the closed heating chamber to a 1 e erences coffeeinfusion chamber for timed infusion, where the UNITED STATES PATENTSheated water is contacted with coffee grounds and 1,916,369 7/1933Harpster 99/282 passed from the infusion chamber to a receptacle to3,405,630 10/1968 Weber 99/286 collect the finished coffee infusion.

R25,663 10/1964 Bunn 99/282 2,346,389 4/1944 Peters 99/282 5 Claims, 24Drawing Figures Pmmm z 3,793,933

sum 1 or 7 2/3 INVENTOR. ROBERT L.WE.BER

BY 22/ l 222 ATTORNEY PAIENTED 2 1 3.793.933

' sum 3 or 7 229 FIG.I| 22 12.2;- A g 3 NOV AC 6O CYCLE INVENTOR. ROBERTL. WEBER ATTORNEY PATENTEDFEBZS'QH 3,793,933

SHEET h 0F 7 l INVENTOR. 3 430 ROBERT L. WEBER 242 ATTORNEY BY 4% WPATENTEmmzs 1914 SHEET 6 BF 7 INVI N [0R ROBERT L.WEBER W ATTORNEYCOFFEE INFUSION APPARATUS AND METHOD BACKGROUND OF THE INVENTION In myprior patents U.S. Pat. No. 3,405,630, issued Oct. 15, I968, U.S. Pat.No. 3,361,052, issued .Ian. 2, 1968, U.S. Pat. No. 3,423,209, issuedJan. 21, 1969, and U.S. Pat. No. 3,518,933, issued July 7, 1970, I havedescribed coffee makers with various attributes which aim forachievement of the objective of obtaining optimally infused coffeelThere are 21 identified defined variables in the making of a coffeeinfusion and, where the product, that is coffee infusion, is as delicateand sensitive to flavor deterioration as a fine wine, it is importantthat attention be paid to details in the making of the coffee infusion.Optimized temperature of infusion is highly desirable and this isidentified as being in the range of 195F i F. (905C i 3C). Protection ofthe infusion and the grounds from oxidation, while they are in contactwith each other, is another important variable. Hence, submergence ofcoffee grounds in water and a single pass through the coffee grounds,away from oxygen, is a desired objective.

As a basis of reference I use the publication of the Coffee BrewingInstitute identifying its standards, objective and subjective, for themeasurement and evaulation of the properties of a good cup of coffee.Reference may be had to its literature, particularly its standards forthe preparation of aqueous infusion of coffee.

It should be understood that in aiming to achieve optimal brewing ofcoffee, my apparatus is concerned with the manipulative processvariables and is not concerned with the condition of the bean itself.This involves an independent group of variables which is determined bythe quality of the raw bean, its ripening, its treatment in the courseof progress from the coffee bush to the product which appears on themarket, and the technique used in the roasting.

It is, accordingly, a basic object of this invention to provide anapparatus suitable for the consistent preparation of an aqueous infusionof coffee with optimized flavor of the infusion, using an appliancewhich is a selfcontained unit, putting under automatic control certainof the variables which can be put under control, other than the natureand quality of the bean itself.

It is a further object of the invention to provide an appliance in aform suitable for ordinary domestic use, but, nevertheless, in acapacity such that it can be made larger or smaller for very nominal useor enlarged domestic use, the unit being such that the variables ofwater temperature, temperature of extraction, time of extraction, andthe protection of ground coffee bean from oxidation during extraction,are set and not subject to abuse by the user of the apparatus.

It is another object of the invention to provide a unit, having aself-contained capacity for correcting one of the major sources of poorflavor in coffee infusions, namely the water itself the correction beingin the form of a filter unit suitable to remove foreign ingredients fromthe water which is used for the preparation of the infusion.

Other objects and advantages of the invention will, in part, be obviousand in part will appear hereinafter.

DETAILED DESCRIPTION OF THE INVENTION The invention accordingly isembodied in an apparatus, and in the corresponding method, whichcomprises a self-contained unit consisting of four identifiable majorcomponents, namely, a base including a water heating chamber, a top, acoffee infusion chamber, and water conditioner, the parts beingcoordinated into a whole, such that the base carrying thefilter-waterconditioner contains the water reservoir, heater,temperature control, and the top receives the water con duit and carriesmeans for supporting the infusor, the infusor being equipped to carry anappropriate amount of ground coffee beans for extraction and developedso as to enclose the grounds away from air, permit submergence in waterand restrict flow of the water therethrough to develop a controlledtimed infusion. The bottom of the appliance is the base which containsthe several controls for heating the water, releasing it at theappropriate time, and communicating with the coffee infusor via aconduit in a closed system, the infusor being mounted in the top and inposition to discharge the infusion at a controlled rate through acontrollable orifice into the receptacle for the finished product.

The invention, accordingly, is embodied in the apparatus and the methodwhich embodies the infusion of coffee involving the combination ofelements and arrangement of parts in the apparatus to be described, andin the method which involves the sequence of steps and coombinations ofsteps and control and adjustment of variables, hereinafter to bedescribed in greater detail.

Referring now to the drawings,

FIG. 1 is an overall perspective rendition of the completed unit showingthe receptacle in place for receiving product with the coordinated partsin the form of an appliance, such as is suitable for use in domesticbrewing of coffee;

FIG. 2 is a section through FIG. 1, longitudinally, essentiallycentrally along line 2-2, showing the several parts of the apparatus intheir coordinated relationship;

F 16. 2A is a perspective view of a control valve in the apparatus ofFIG. 2;

FIG. 3 is a plan view of the main switch of the apparatus through whichthe sequence of operations is controlled;

FIG. 4 is a detailed sectional view of the skeleton of the top pieceshowing the relationship of the several parts to each other;

FIG. 5 is a detailed view of the discharge orifice o the coffee infusionchamber itself;

FIG. 6 is a plan view of the head and quick turn-on support for thecoffee infusion chamber;

FIG. 6A is a plan view of the coffee infusion chamber.

FIG. 7 is a bottom plan showing the base structure; FIG. 7A is a topplan view of the base structure, with the overlying parts removed.

FIG. 8 is a diagram of an electrical circuit for use with the appliance.

FIG. 9 is a section vertically showing a bushing providing a connectionfor a water tube in the appliance.

FIG. 10 is a section vertically showing a connection of a head to a basein the appliance.

FIG. 11 is an enlarged view of the control switch.

FIG. 12 is a section vertically through a model of the apparatus showinga second embodiment similar to that shown in section in FIG. 2, whereinthe coffee infusion chamber, top safety valve, and heating arrangementin the base have been modified to a preferred version;

FIG. l3, 14 a and b and 15 are coordinated to show the mechanicaldetails of the structure of the switch;

FIG. 13 being a plan view thereof; FIG. 14 a longitudinal section; FIG.14a a perspective of one slide; FIG. 14b a perspective of a secondslide; and FIG. 15 a bottom plan view.

FIG. 16 is a diagram of the electric circuit used in the base of thedevice.

FIG. 17 is an enlarged showing of the structure of the safety pressurerelief valve formed as part of the top;

FIG. 18 is a showing of the water discharge tube to take water from theheating chamber up through the column and to the infusion chamber.

FIG. 19 shows a flexible connection between a relatively rigid waterdischarge tube for the heating chamber and a relatively rigid inlet tubeleading to the infusion chamber.

Referring now to FIG. 1 and 2, the appliance consists of a base 100formed with a generally elliptical outline and, in this illustration,shown with a serrated bottom edge 101 carried by a downwardly dependingskirt 102, integrally formed with a recessed top 103, which in turnjoins the integrally formed upstanding section 104 in the narrow end ofthe ellipse forming the base outline. This unit is formed thus,generally tapered upwardly and styled so that it can be of a plasticsuitable for molding in asingle operation.

As shown in vertical section in FIG. 2, the upstanding section 104 isformed with a ledge 105 near its upper end,.from which it continues assection 106 to terminate in threads 107 and cap 108. Fitted onto thebase, at the upstanding section thereof, is the head 109 again formedasa single integral piece. The head 109, is partially covered by top 111which can be snap fit. This to provide access to the interior. The head109 is also styled and shaped to slide fit on the upwardly extendingcolumn 104 of the support base 100 specifically the narrowed end 106 torest on ledge 105 and form a continuous exterior line, preferablycarrying upward the stylish shape given to the overall exterior of theunit.

As shown in FIG. 2 the base 100, in section, is seen to consist of aslightly upwardly tapered exterior shell 100 integrally molded with aninternal wall 102a partly closed by the a top 103 which is recessed toprovide a support on which a receptacle 201 for coffee can rest. Fins13' are molded on the inside of top 103.

It will be seen that the lower edge 112 of the internal wall 102 a iscurved and matched by the form of the edge of a base plate 113 which isformed with an edgegroove to conform and fit around the edge 112 of thewall and extend to the outer wall of the base 100. A sealant 114preferably, Dow Corning 732RTV silicone rubber, is compressed betweenthe edge 112 of the wall and the base plate 113 to provide a waterproofseal. The base plate 113 is held in place by a sequence of screws 116,117, etc. The screws are set symmetrically around the circumference ofthe bottom and hold the base plate in place in a water-tight joint.

Base plate 113 is formed with. a depression 113, therein, in which ringheater 121 is carried. A larger ring heater 122 is carried in the mainbody of water in the reservoir base of the containen The reason for thesmall heater and the depressed pan constituting a small reservoir issafety in providing a source of heat absorption for the ring heater 121.

The ring heater 121 and 122 are part of the electrical system which isseparately described hereinafter.

Fixed to the inside surface of the depression 113' in the base plate 113is a four-pronged retainer 123,

which serves as a support for a control valve 131 (see FIG. 2A). One endof a coupling nut 132 is connected to a tubular discharge outlet 133. Aretainer element 134, is closely fitted around the other end of the nut132, and is formed with outwardly extending flange 135, having itsperiphery curved to receive a temperature responsive bimetallic disk136, carrying an adjusting screw 137, which supports a valve 138cooperating with a seat 139 formed in the coupling nut 132. Openings 141are provided at quadrants around the circumference of the flange elementto permit water to pass through the valve. The temperature responsivedisk 136 is set to snap sharply in a direction to open the valve 138 inresponse to water reaching the temperature of infusion which is soughtand in the manfuacture of this unit, this metal snap valve will be setto respond sharply to a temperature of about 195F.

Referring now to the upstanding section 104, it will be seen to includea single tubular member 151, having its bottom edge 152 rolled aroundthe periphery of a stainless steel strainer 153, to form a filter base.The upper edge 154 is rolled or flared outwardly to match the curvatureof the top edge of the upstanding tubular section 104. A gasket 155 iscompressed between the cover 108, and the upper edge of tubular member151, to form a water-tight seal. The outer circumference of the cap 108can be knurled to permit simplified gripping thereof when it is screwedinto or out of place.

Centrally in the cap 108 is an orifice 161 and within the cap is adownwardly depending cylindrical neck 162 aligned with the orifice andthreaded to receive a stainless steel retainer 163. Orifice 164 inretainer 163 is carefully calibrated to match the weight of a valve 165,having a tapered conical end cooperating with the orifice, which acts asa safety valve. That is, should any failure in the heating system occurto produce overheated water, this is a simplified safety valve torelease excess vapor pressure. It is preset for the vapor pressure ofwater at just below the boiling temperature, i.e., about 200F., andworking in conjunction with ring heater 121 maintains a constant vaporpressure during the extraction period.

Water connection is made from the control valve 131 to the infuser 191,through the tubular memmber 133, which is connected to the valve 131, atone end, conducted around the side of the filter chamber, and throughthe hollow head 109 to the infuser.

The filter chamber 151, which is enclosed in the water chamber, isfilled with an appropriate filter material, generally activated charcoalis suitable, using granules about as finely divided as ground coffee.Its function in the device is to remove components from the water whichadversely affect the flavor and aroma of coffee. Water is poured inthrough the top. In a single pass through the filter bed, chlorine,fluorine, iron, phosphates, and other chemicals are removed from thewater. By including ion exchange resins, or deionizing resins, it ispossible tocondition the water and to have it completely free of anykind of chemical, whether naturally occurring or present as a pollutant;particularly it is possible and desirable to remove from the water, bythis filter arrangement, the extraneous components to the point ofmaking the water deionized. It should be conditioned to avoidinterference with the flavor of the infusion.

The head of the unit which I have generally designated 109 is a singleinjection molded piece shown in additional enlarged detail in FIG. 4.Basically the head consists of the member 109 elliptical in periphery,integrally molded with an internal circular cylindrical section 181,which fits around section 106 as a support, the internal portion of thehead 109 also having a curved, guide section 182. Guide section 182 iscurved inwardly and upwardly to terminate in a low conical top section183 which has a inner downwardly depending inner ring 184 molded thereinto define with the guide section 182 a groove 185, in which a gasket 186isseated. The top section 183 formed as part of the head is sealed atits open apex around a stainless steel fitting 187 with an O-ring seal188, to provide a point of entry for the water from water inlet tube133. Top section 183 has molded therein a set of several fins 183' toserve as spacers for a screen 189 and also as water spreaders.

The coffee basket or infusor, in section in FIG. 2, and in plan in FIG.6A consists of the single molded unit 191, having slightly conicallydiverging sides with the sequence of lugs, 192, 193, 194, 195, 196, 197,198, and 199, integrally molded into its body near the upper edge. Thiscontour of infusor 191 is matched by the top section 183, where openings261, 262, 263, 264, 265, 266, 267, 268, (FIG. 6) receive correspondinglugs and guidethem into locking position with a quick turn of a smallfraction of a circumference. Two lugs 201 and 202 on the side of infusor191 are made enlarged to provide a manual grip. For close sealing of thecoffee basket in place, gasket 186 is provided in the groove 185 in thehead 109.

Within the coffee basket on its bottom 213 are molded ribs 214, 215,216, 217, to the number it may be considered desirable to have, whichsupport a steel screen filter 218. A paper filter may also be provided.

The oulet from the coffee basket is through an integrally molded nipple221 (FIGS. 2 and 5) and a flexible plastic fitting 223, which may bemolded of polyethyl ene or polypropylene, snap fitted on the nipple 221.The fitting 223 has a fixed central orifice 219 (FIG. 2) and ahydraulically parallel variable orifice comprising a laterally directedopening 225 providing fluid communicationbetween a contoured recess 222(FIG. 5) and a central opening 224 in the fitting 223. Orifice 219 alsocommunicates with opening 224. The fitting 223 is rotatable in positionon the nipple 221, so that orifice 225 in one position can see auxiliaryspace 222 to provide for extra flow, e.g., for six cups, and in the nextposition the orifice 225 can see space 222 to permit eight-cup-flow,under the pressure conditions for which the apparatus is set. That is,with a fixed total volume of apparatus, i.e., water chamber and coffeebasket, it is important that the residence time of water in the coffeebasket be kept approximately constant, whether the apparatus is used forfull eight-cup volume, or six-cup volume or four-cup volume. This isdone by maintaining constant pressure within the device but providingvariable capacity for outflow. This of course is net outflow of coffee.The water measurement allows for that retained in reservoir 113' and theholdup in the coffee grounds in the coffee basket.

The water connection from valve 131 to the water basket at the top ofthe apparatus is made by tube 133 which, as indicated in dotted lines inFIG. 2, extends from valve 131 over to one side of the apparatus upthrough the hollow upstanding element 106, beside the filter, through anopening in the head 181, across to the fitting 187, to connect theretowithin the head. The entire unit is covered by the top cover plate 111.Fitting 187 is essentially an elbow formed to receive water tube 133,and turn the water to a downward direction. Exit from fitting 187 is viaorifice 187 which is slightly flared to receive O-ring 188, and form asnap fit with the head 183.

The coffee receptacle 201 consists of the container equipped with apouring spout 202, handle 203, and cover 204, with an opening 205, toreceive coffee discharged from the basket.

In the operation of making coffee, the appropriate volume of water ismeasured into the calibrated container 201, poured through the open topof section 106, from which cap 108 has been removed, to pass through thetubular member 151, and drain into the vessel defined by base plate 113and wall 102a. Cap 108 is replaced and the water is then heated to theappropriate temperature. The internally developed pressure, due toheating, will be sufficient to force the water past the valve 131, assoon as the valve opens and through the tube 133 to the coffee basket.

Since it is desired to have the device function automatically in anon-off operation the electrical heating system, as indicated in FIG. 2,is built into the bottom of the unit and consists of power supplyconduit 21], passing through insulator 212, to bring leads 413 and 414,to control unit 215 to provide energy to the two heating rings 121 and122. The control unit 215 is shown in vertical section in FIG. 2 andpartly in FIG. 11, and in detailed plan in FIG. 3. It includes abimetallic heat responsive element 421, attached at one end to the baseplate 113 of the reservoir. A support plate 422 has four upstanding arms422a welded to the under side of the base plate 113. A switch operatingmember 423, having a push button 425 at its right-hand end, slidesbetween plates 113 and 422 and, at its left end, carries a latch lever226, pivoted at 227 (FIG. 11). The righthand end of lever 226 isconnected by a spring 229 to a lug 230, bent upwardly from plate 422. Athickened part 231 of the plate 422 carries two adjustable detents 232and 233. The lever 226 has at its left-hand end a tapered finger 226awhich cooperates with bimetallic element 421 and at its right-hand end afinger 226b which cooperates with detents 232 and 233. The switchoperating member 422 carries cams 243 and 244 (FIG. 3), which operatemovable contacts 235 and 236, cooperating respectively with relativelystationary contacts 234 and 237. When the switch operating member 423 ismoved to its extreme left-hand position, finger 226b engages detent 232,cam 243 closes contacts 236 and 237 and cam 244 closes contacts 234 and235.

When the water reaches infusion temperature, bimetallic element 221moves finger 226a, rotating lever 226 counterclockwise enough to liftfinger 226b upward off detent 232. Spring 229 then moves the switchoperating member 423 to the right and rotates lever 226 clockwise toengage detent 233. In this position of member 423, contacts 234, 235,remain closed, but contacts 236,237 are open. The member 423 holds thatposition until the water reaches a still higher temperature, at whichbimetallic element 221 again engages finger 226a and rotates lever 226counterclockwise to lift finger 226b off detent 233, whereupon spring229 returns member 423 to its off position.

In FIG. 7A, it might be seen that the base 100 has an arcuate peripheryat its right end, merging tangentially with an elliptical periphery atthe left-hand end. The upstanding section 104 supports the tubularmember .151. The ledge 105 extends between the upstanding section104 andthe elliptical periphery of the base 100. Two openings 105' and 105" areprovided in the ledge 105. These openings are matched by similaropenings molded in the head 109, and provide a means for fastening thehead securely onto the base. This is accomplished by the structure shownin FIGS. 9 and 10.

In FIG. 10, which is a section vertically through the fastening, headpiece 109, and ledge 105 are shown as fastened by a bolt 251 and nut255, cooperating with washers 252 and 253, and an O-ring 254, to form apressure liquid-tight joint when the nut 255 is fastened into place.

The opening 105' and 105" are made symmetrical because the opening 105"as shown in FIG. 9, serves as a passage for the water tube 133, from thebase up through the hollow space, through opening 105" and therefrominto the head and coffee infusor. The head 109 and ledge 105 arefastened together by a bushing 261, a gasket 263, and a nut 264, tocompress an O-ring seal 265, and form a watertight joint. It isimportant to observe that the water reservoir in the base of theinstrument, from base plate 1 13 to the ledge 105, is a single unitarycompartment within which the water is heated and vapor pressuregenerated. Thus, the head 109 is securely and stably fastened in placeon two sides of the upstanding section 104. By providing the watertightand moderately pressure-tight joints, it is possible to heat the waterin the reservoir and thereby develop sufficient pressure to drive itthrough the tube. A moderateamount of vapor space above the water levelis needed to act as a pressure accumulator, thereby storing vaporpressure energy during the heating cycle.

FIG. 7 shows the structure of base 100. A sequence of bosses 102' ismolded between the skirt 102 and the wall 102a. By providing asufficient number of these bosses, adequate connection is made forsecurely holding the bottom 113 in place'when it is fitted to the edgeof the wall 102a and tightened in place by the sequence of screwsindicated as 116, 117 (FIG. 2),.

In FIG. 6, and in FIG. 4, I have shown, respectively, a plan andsectional view of the single molded piece which serves as the head 109on which is carried the coffee basket 191 (FIGS. 2 and 6A). Thus thehead 109, as a single molded piece, is shown with the cylindricalsupporting left end and slightly tapered outer surface, together withthe basket-carrying potion, having the inwardly sloping curved surface182.

The curved surface 182 has a sequence of apertures therein 261, 262,263, 264, 265, 266, 267, and 268, around its circumference. Theseapertures are molded to provide a point of ingress for the lugs on thecoffee basket and by means of a quick one-eighth turn, the lugs of thecoffee basket ride up cam surfaces at 271, 272, 273, 274, 275, 276, 277,and 278, to form a firmly engaged joint, thereby compressing gasket 185and sealing head 109 to coffee basket 191 as shown in FIG. 2.

Dimensionally, these apertures and cam surfaces can be molded to a finedegree of tolerance as can be the lugs on the coffee basket. Hence, inproviding entry for the lugs the curved surface 182 provides a guide,and when the user feels the coffee basket enter the unit, a

quick turn in the direction indicated, actually a oneeighth turn,fastens the basket firmly in place.

Under a given constant pressure, such as will be developed in the waterreceptacle when the water is heated to 195F. it is important that thewater pass through the coffee grounds in an approximately fixed orprefixed period of time, e.g., about three minutes. With a small volumeof coffee grounds and a small volume of water, it is desirable to varythe size of the opening because all other variables have been fixed bythe apparatus. FIG. 5, the bottom 213, on the coffee basket is shownenlarged.

DETAILED DESCRIPTION OF THE CIRCUIT In FIG. 8 I have illustrated insemi-pictorial form the circuit which is employed for the two levels ofheating in the water heating chamber.

For coordinating FIG. 8 with FIG. 3 and FIG. 2, where the pictorialrepresentations of the switch and the heater in place are shown, I haveused identification numbers on the circuit of FIG. 8 to correspond withparts in FIGS. 3 and 2. Thus, the circuit consists of a two-levelheating circuit in which power is supplied by line 211 with a branchconsisting of line 238 to heating coil 122, high level, generally for aneight-cup infusor 1150 watts, lead 239 to switch contacts 234 and 235.The parallel coil consituting the low-level heating, for example, 350watts is fed by line 240, to heating coil 121, with return by line 241,switch 236 and 237.

Shown diagramatically, in this circuit, is the switch 425 with the cams243 and 244 diagramatically related to these switches to correspond topoints 234, 235, and 236, 237 of FIG. 3. When the switch 225 is moedforward to its most forward point so that finger 226b engages detent 232(FIG. 11), both switches 236 237, and 234, 235 are closed and heating ofthe water in the infusor with both circuits in total of approximately1,500 watts is in effect. When a predetermined temperature is reached,bimetallic element 221 engages finger 226a and rotates lever 226, movingfinger 226b off detent 232 from which position it moves to detent 233and is there held. When finger 226b moves off detent 232, the circuit tothe high-level heater, namely the 1,150 watt or the circuit 122, isopened at contacts 234, 235 and the heat supply holds at the 350 wattlevel which is sufficient to maintain temperature and to generate theadditional vapor needed to move the whole body of water to the infusor.

After the water level drops to the small amount left in the reservoir113', being heated by heater 121, the temperature is raised further tocause the bimetallic element 221, again, to engage feeler 226a androtate lever 226, moving finger 226 b off detent 233 and causing theswitch to drop back to the off position. In this manner the heating ofthe water is completed; the water is driven through the infusion cup,and upon completion of the operation the device shuts itself off.

FIGS. 12-17 Referring now to FIG. 12 it will be apparent from thesection that the overall structure of the device and combination thereshown corresponds to that in FIG. 2. The modifications making this thepreferred version are in the improved infusion chamber, which providesfor a constant residence time of water in the chamber, whether theamount of coffee being made be four, six or eight cups; an improved topfor the column to close the water vessel, which incorporates a safetyvalve; and improved water release mechanism in the base.

The method of brewing coffee requires the accompanying switch mechanismto be sharply temperature responsive so that the high intensity heatused to bring the water up to infusion temperature can be dropped to alower intensity to maintain the water temperature for discharge. It canfurther provide for a heating circuit in the base of the appliance underthe coffee receptacle.

For convenience in reference and identifying parts, the numerals used inFIG. 2 identifying the basic parts of the apparatus have been carriedover to FIG. 12. The details of modifications are shown by the adoptionof a new sequence of numbers in reference to the modified part:

In the column 104, filter tube 151 is centered by ribs 106' spaced onquadrants and at its top is flared to rest on the ribs below the cap108.

For purposes of developing a constant residence time of hot water in thecoffee infusion chamber I have found it preferable to utilize themodified basket as shown in FIG. 12, wherein the top 183 has a modifiedmolded central bushing 250 having a side inlet 451 threaded to receive awater tube 452, which here is shown terminating in a small nipple 453,which makes connection with the vertical through a flexible elbow 133".The details of this connection are shown in FIG. 19.

Centrally in the bushing 250 there is molded a nipple 454, which isthreaded to receive screw 455, the nipple being central in the bushing250 to define a circular torus-like orifice 256. Fastened to nipple 454by the screw 455 is the water spreader plate 257, which is a metal diskcarrying perforations spread over the entire area of infusion. Theperforations should. be sparse near the center to be sure to developspreading of waterto the periphery. This spreader plate 257 is fittedwithin the downwardly depending skirt 184, which is slightly undercut toprovide a snap fit for the spreader plate. A further securing of thespreader plate can be obtained by fitting a split ring 258 within theundercut groove.

The coffee basket which forms the infusion chamber consists of thestraight sided cylindrical unit 260, having a conical bottom 461terminating in the central orifice 262 with a set of internal integrallymolded bottom fins 263, the number to suit the designer but generally,eight. These are to assist in developing easy passage of the freshcoffee infusion.

The radially spaced fins are also suitable to support thescreen filter464 which also serves as a support for a filter paper 465 on its upperface. Three internal interchangeable adapters for setting the amount ofcoffee grounds to match the volume of coffee infusion to be made areprovided. Thus the adapter 266 shown in full section, has a verticalheight which defines the volume for coffee grounds and terminates withan outwardly flared portion 267 and an upwardly directed circumferentialrim 268, which just fits within the receptacle 260, to be receivedwithin the annulus 185 defined by the downwardly depending skirt 184,and form a water tight joint against the gasket 269.

Insert 271 has the same form but is of greater diameter. Inserts likethis serve to define the volume of grounds to be used within theinfusion portion of the device and at the bottom circumference to form aclose fit against the filter paper 265 and screen 264 to provide a waterseal. At the top, the water distribution is through the tube 252 tostrike spreader plate 257, which spreads the water in a patternthroughout the entire area of the top causing it to submerge the coffeegrounds and keep them submerged in water, shielded from air during theinfusion, without the inducing the formation of channels in the bed ofcoffee grounds.

The exact volume of coffee to be made with the adapters, depends uponthe actual size of the appliance to be used. For convenience and as anestimate of a reasonable size for use in ordinary domestic applicationsI have found that the four cup and six cup inserts are useful with acoffee infusion chamber which has a maximum design for eight cupswithout an adapter.

The insert which fits within the infusion chamber 260 serves thefunction of holding the filter paper and screen in close juxtapositionin the bottom of the infusion chamber when full capacity is beingbrewed.

A cover plate 113" to cover all parts is fitted within the innerperiphery of base a snap fit being useful.

The heating mechanism and water discharge in this embodiment arecentered around the formation of the valve, which is best inspected fromthe discharge tube 133 which in this instance terminates in a flared endnipple 133'. The valve, shown in section in FIG. 14, consists of a valvecasing 300 having formed therein holes such as 301, 302, and 303 toprovide for discharge of water. The valve casing is flared outwardly toa disk 305 which has a threaded edge 306 which is threaded into abushing 307 fixed in the depression 113' in the bottom of the container.As shown in section in FIG. 14, the valve body 312 has vanes 308, set atright angles to each other, and integrally molded, preferably forexample of Teflon, with the body 312, which seats against a shoulder onthe casing 300. A bellows 313 is also integrally molded with the valvebody 312. The bellows is angularly flared to form flange 314, as shown,and fitted against a shoulder 315 of the valve body and fastened inplace by ring 316. Bimetallic disk 317 is held centered by the adjustingscrew 318 and lock nut 319 and fastened in place in an undercut grooveof the valve casing by a splint ring 3170.

The valve casing 300 is fitted into the flared nipple 133' of thedischarge tube and the seal is formed by the O-ring 300a.

The bimetallic disk may be any combination of metals which will developthe movement desired. Stainless steel clad with copper is suitable andwith adequate dimensioning, change in direction of curvature can be hadat a closely determined temperature.

The purpose of this construction is to give the valve body thelongitudinal movement to open and close it. The bimetallic disk sensesthe hot water and by differential expansion at a given temperature willsnap the valve open downwardly by the buckling of the curvature of thedisk. The autogeneous pressure within the closed chamber will forcedischarge of water through the tube 313. The movement of the screw 318,which is also an adjusting calibrating screw, is employed to actuate aswitch in the electric heating circuit, through any desired mechanicalarrangement. One arrangement has been shown in connection with FIG. 2.The preferred arrangement shown herewith is like that in FIG. 2, builtto provide a heating at an intense level to bring the water up totemperature and a second stage of heating at a lower level to hold thewater at temperature to push it up to the infusor. If desired a thirdlevel can be provided to keep the coffee warm in the receptacle.

For a mechanism useful for controlling the heater circuit, reference maybe had to FIGS. 13, 14, 15. Thus, the external thumb operated pushbutton segments 320, 321 (FIG. 12) which for purposes of convenience canbe semicylindrical in form are enclosed within the tubular support 322which carries the bracket supports 323, and 324 to permit mounting it onthe base of the water heating chamber by a spot welding operation. Acylindrical barrel 325 carrying eccentric cam 326 to provide forselection of a four cup, six cupor eight cup heating intensity circuitis indicated. Connection to the circuit can be made by any conventionalmeans. The mechanical manipulation of the switches is partly by means ofthe thermally responsive bimetallic 'disk 317 and partly by thebimetallic actuator 327, which for purposes of fine control can be madeof two different bimetallic elements fastened together by a pin 328. Thefunction of this mechanism is to develop a certain movement and whatevercombination of bimetallic elements develops that movement will serve thepurpose.

This mechanism is illustrated in the detailed FIG. 14 wherein thebimetallic element 327 is shown, with the thermally responsive disk 317in section and the screw 318 is operative relation to the switch device.

The switch mechanism thus consists of the two manually operable pushbutton segments 320 and 321 which are of different lengths and have endslots which individually actuate the moving parts of the switchmechanism. Thus segment 322 actuates an upstanding-arm 330 which isinsulated by plastic sleeve 331 (FIG. 14) from the switch contact 332,which it operates. Similarly, push button segment 321 actuates theupstanding arm 335 and operates contacts 336 and 337.

The switch contacts 332, 333, 334, 336 and 337 and their supportingfigures are insulatingingly mounted on a support 340 shown in FIGS. 13and 14. The upstanding arm 330 is a part of a slide shown in FIG. 14a,having an upper horizontal portion 341, a middle horizontal portion 342fitting under the support 340 and a lower horizontal portion 343 whichextends under the screw head 318 actuated by the thermally responsivebimetallic disk 317. A finger 334 is bent downwardly from the middlehorizontal portion 342 of this main heater slide. Spring 345 (FIG. 15)has one end fixed on the end of an arm 346 of the support 340 and itsopposite end is caught under the finger 344 on the main heater slide.The spring 345 biases the main heater slide to a position in which thestep between slide portions 342 and 341 is held tightly against the edgeof an opening in the support 340. In this position of the main heaterslide, which is shown in FIG. 13, all the switches are open.

The second switch slide (FIG. 14b) for the auxiliary heater is formedwith the upstanding arm 335, and a horizontal section 351 extends underthe support 340, terminating in an arcuate bend 352, which serves as aspring, and in which adjusting screw 353 is set.

For convenience in and clarity of understanding the operation andconstruction of the device the outlet valve 300 of FIG. 12 has beenpositioned in FIG. 14 in enlarged section and operative relation to theswitch slide structure.

The slide operated by arm 330 is mounted on the support 340, whichsupport has openings 360 and 361 to permit movement of the slide partstherein. The support 340 carries a detent pin 362 placed to engage aknife-edged opening 363 in slide portion 342. Similarly, the slide 351which is shown in reduced perspective in FIG. 14b has an opening 37stamped therein and provided with a knife-edge to engage a detent 371.

In operation the main heater push button segments 320 and 321 aremanually pushed inward, the total motion for a full scale domesticappliance being approximately one-fourth inch with the result that thesegments exert horizontal forces on the arms 330 and 335 moving the twoslides to the left, closing the electrical contacts to bring aboutheating of the water in the reservoir. The openings in the respectiveslides engage the respective detents 362 and 371 and the contacts areheld closed. When the appropriate temperature of the water is reached inthe base of the container, the bimetallic snap disk on the valve 300senses the temperature, snaps the valve open and the screw head 318 in aproperly adjusted valve will move longitudinally downward, total motionabout 0.050 inch, to engage the main heater slide and dislodge it fromthe detent 362 causing the slide to move back to an off position andopening the circuits completed by switches 334,333,332. The reducedintensity of the heater remains on to keep the water moving and whenmost of it has been moved out of the heating chamber, or all of it hasbeen moved out, bimetallic element 327 will have reached and moveddownward to engage screw 353 to move it and disengage the correspondingknife-edge opening 370 from the detent 371 allowing the auxiliarycircuit then to snap to the open position, being moved by a spring 401corresponding to spring 345.

The relative positions of these parts are shown by reference to FIGS. 13and 15 which are top elevation and bottom elevation of the switch unit,showing the switch terminals A, B, C, D, and E and their relation to thecontacts.

Reference to FIG. 16 will show the electrical circuits connected to A,B, C, D, and E indicating that there are two intensity levels for thecircuit, A, B, C, to be selected by the cam on the switch manipulator.In FIG. 16 this is shown as an ordinary volt, AC, 60 cycle, circuit usedwith two heater branches. I have found 650 watts and 230 watts usefullevels. By making line A common to the termainal A, it will be observedthat terminals B and C close circuit therewith the main switch slide.The auxiliary switch slide closes circuit D-E. The selector can be inthe form of a mechanical selector a manual switch 402 shown in thediagram, with selector positions for four, six and eight cups, theintensity levels which would be desirable for a typical domesticappliance.

FIGS. 12 and 17 show a top 108 having an internal safety valveconstruction Centrally molded as part of the top 108 is the top opening375 and a downwardly depending tube 376 having a threaded end in whichis fitted a retaining ring 377. The valve insert consists of api-section, hollow unit 378 having side vanes 379, 380, runninglongitudinally along it to guide it in the opening, its bottom extendingacross substantially the entire diameter of the downwardly dependingbushing 376. Its tip is formed of a rubber gasket material 383.

The pi section portion of the valve is urged into close sealingrelationship with a seat encircling an orifice 377 by spring 385 whichbears against a shoulder in the tube 376. Retained on orifice 386 is thecylindrical stylus 390 having soft (rubber) tips 391 and 392, to permitinserting it either way. The weight of this stylus 390, with its gasketmaterial tips 391, is selected to form a pressure relief valve at theorifice 386 to correspond with the vapor pressure of water at atemperature of just about boiling. Inasmuch as actual discharge from theheating chamber will occur at a temperature just below the boil, in usethe stylus 390 will usually chatter slightly in position. This is apreferred form of operation, becuase it indicates appropriate pressureis being reached and maintained in the water heating chamber. In theevent of failure of the stylus 390 'to lift to relieve pressure, thespring and valve portion around it are set to open, or cause the pivalve to open, at a pressure a few ounces per square inch above thevapor pressure of water at the boiling temperature. This is a safetyfeature and once the valve lifts against its spring the vapor escapesaround the tip around the spring, and out through the orifice 375, andout the top of the unit. The valve face serves to provide a certainblowdown allowing the vapor pressure within the vessel to drop to a safelevel before the valve will be reseated by the spring.

The preferred version of the water tube is shown in FIGS. 18 and 19. Thewater tube is a three piece unit in which the bottom end 133 is flared,bent suitably to bring it to a point to be passed through the ledge 105to terminate in an upwardly directed open end in the column 104. Thisend is connected to the water inlet tube 452 of the coffee infusionchamber as indicated in FIG. 19, employing a simple, flexible elbow 133"with spring clips to make tight joints.

Reference back to FIG. 12 will illustrate an optional form of rest forthe coffee receiver which is positioned below the orifice discharge ofthe infusion chamber. This receiver, generally in the form of a glass orsteel pitcher, will rest on the plate and for the convenience of theuser it may be desirable to build into the plate a warming coil. Hence,the water heating chamber shown in FIG. 12 has a top 400 with a recess401 molded therein to receive a coil heater 402. A stainless steelcover- 403 is snap fitted in place over this. A temperature sensingelement 404'is fitted within a recess 405 molded in the top 400, andcovered with a flexible metal shield 406. Electrical leads from theheater 402 and sensing element 404 can be brought through the groove 407provided therefor, down through the side of the unit for connection intothe electrical circuit.

In operation the cycle sought is a quick heating of the body of water tobe brought to infusion temperature, a quick release of the valve closureat appropriate infusion temperature, provision of enough space withinthe water heating chamber to provide a significant volume of vapor andair to expand and provide the driving force for lifting the waterthrough the tube 133 from the valve up through the tube and into thecoffee infusion chamber. The coffee infusion chamber is designedpreferably to give an optimum infusion time and depth of coffee grounds,these two variables being interrelated. Hence, the water distribution isprovided over the bed of coffee grounds,'the grounds being of anappropriate depth so that the entire volume may be quickly wetted by thehot water.

Overall in using the circuit for the capacity indicated, for makingeight cups of cuffee, l have found that the calibration of the containershould be such that a few ounces of water should be allowed for holdupto wet the body of coffee grounds, representing a loss in volume. Foreight cups of coffee about to 51 ounces of water are provided this beingcalculated at 6 ounces per cup, with about 2 to 3 ounces holdup.

The filtering of the water to condition it for preparation of the coffeeis by adding it through the top 109, as a consequence of which itpercolates down through the column of activated charcoal, which shouldhave a degree of granularity approximately that of ground coffee. Anylaboratory grade of activated charcoal is suitable, such as chemists useroutinely in laboratory work for decolorizing solutions. Since chlorineand fluorine ions are perhaps the most seriously detrimental ones to theflavor of coffee, and are virtually universally used as water additives,it is important that the filter material be suitable to pick up chlorineand fluorine ions. Beyond this, if the water is very hard and containslarge amounts of metal ions provision should be made for removing these.Perhaps an ideal would be deionized water. Hence, synthetic resins ofthe type used for dionization of water are also useful as a filtermaterial.

Materials of construction for the appliance are fundamentally dicatatedby the use to which it is to be put. Bearing in mind that it is toprepare a potable beverage and the temperatures will commonly be of theorder of Centigrade of 212 Fahrenheit, and higher in the heating areas,it is important that the materials be suitable for use at thistemperature level, with various grades of water, and to withstand thecorrosion to which they will thus be subjected. For the body of thedevice and the formation of all the molded parts, I have found thatpolycarbonate resins are eminently suitable. A specific resin is onewhich is manufactured by the General Electric Company and sold under thetrademark Noryl 73 1-8. It has the virtue of having the propertiesdesired and is also approved by the Food and Drug Administration asmaterial which can be used in contact with foods. This latter point, ofcourse, is basic to selecting material which is to be used in themanufacture of the appliance.

For the metal parts of the device, namely, the water heating chamber,the heating coils and the tube which is the conduit, as well as thevalve in the enclosure, stainless steel is indicated. Stainless steelcompositions of the so called 300 series which have a very fine level ofresistance to corrosion are most suitable.

The mechanical parts of the switch mechanism for turning the applianceon and off are ordinary carbon steels, spring steels, appropriatelyplated and finished where necessary. The copper leads are conventional.The copper contacts are of beryllium spring copper. Insulators areconventional where they are used.

The heating coils used in the body of water or in heat exchangerelationship with the water, are of conventional construction, such asused in conventional coffee perculaters, that is, whatever comes incontact with the water must be resistant to chemical reaction with thewater. Beyond this, the materials of construction or design are asvariable as may be available to the designer.

Since a basic point in the method of making coffee infusion inaccordance with this invention involves an appropriate time temperatureextraction, the standards of the Coffee Brewing Institute should be keptin mind as to the quantity of coffee and period of time of extraction.The recommended time of extraction is three to four minutes at about F i5. This is variable to suit individual tastes, but this number isaccepted. The amount of coffee to be used per six ounce cup is aboutone-third ounce or grams. Since a cup is accepted to be six liquidounces the volume of water and hence the volume of water heating chamberis indicated. The heating chamber should be of size that it contain themaximum amount of water for the appliance, namely, about 48 ounches foreight cups and still leave a significant air space above that water forthe accumulation of vapor and development of pressure and energy to movewater up through the deliverytube, which is five thirtyseconds inch indiameter (0.6-0.8 cm). In heating and brewing coffee with less than themaximum eight cups there will be that much more free volume and thepushing action the expanding air and vapor will be that much easier.

The time of extraction is developed by the rate at which the water isdelivered to the infusion basket and the rate at which it can passthrough the coffee grounds and run out of the orifice. This is done byregulating the size of the infusion basket to keep the depth of coffeeconstant at about 1 11- l /2 inches in height 3- 4 centimeters). Theheight determines the rate at which the flow occurs and the orifice ismade large enough to allow all of the infusion to pass out as it isformed, i.e., about one-fourth inch in diameter (about 0.65centimeters). The diameter of the basket will vary with the insert usedto match the number of cups of infusion to be made.

What is claimed is:

l. A coffee maker comprising in combination, a base, a water heatingvessel on said base having an inlet and an outlet, means for heatingwater in said vessel, means on one portion of the vessel to support acoffee receiver, a column extending upwardly from another portion of thevessel, a coffee infusion chamber supported by the column, means forclosing the inlet, a passage through which heated water may be withdrawnfrom the outlet of the vessel and passed to said infusion chamberthrough an entrance thereto, a water spreader means disposed across theentrance to said infusion chamber, a thermally responsive valve meanscontrolling said passage for said heated water, said valve means beingclosed when the water is below a preset temperature and being sharplyresponsive when the water exceeds said preset temperature to open saidvalve means and permit water under pressure built up in said vessel byheating of the water therein to pass via said passage to said infusionchamber.

2. A coffee maker comprising a base member, a closable water heatingvessel mounted on the base member, a coffee infusion chamber exterior tothe water heating vessel and spaced above the base member; water inletmeans for the vessel extending therefrom up to at least the top of thecoffee infusion chamber; a closure element for said water inlet means; awater flow tube connecting said water heating vessel from a point nearthe bottom thereof to said coffee infusion chamber; valve meanscontrolling the flow in said tube;

means responsive to the temperature in said vessel for operating thevalve means, said valve means being closed at normal room temperature;means for heating the water in the vessel to increase the pressuretherein when both the closure element and the valve means are closed;said temperature responsive means being effective to open the valvemeans when the water exceeds a predetermined temperature, so that thewater then flows rapidly through the valve means and the tube to thecoffee infusion chamber.

3. Coffee making apparatus for heating selective variable quantities ofcoffeee, comprising a closablepressure-tight water heating chamber, aninfusion chamber, a conduit connecting the heating chamber and theinfusion chamber, a valve controlling water flow through the conduit,means responsive to the temperature in the heating chamber for operatingthe valve from a closed position when the water therein is below apredetermined temperature to an open position when the water exceedssaid temperature, heating means effective when the chamber is closed togenerate pressure in said heating chamber, said pressure being effectivewhen the valve is thereafter opened to urge a measured quantity ofheated water from the heating chamber through the infusion chamber, andmeans to control the flow of heated water through the infusion chamberin accordance with the quantity of coffee to be brewed in order tomaintain a constant infusion time.

4. Coffee making apparatus as claimed in claim 3 wherein the means tocontrol the flow of water through the infusion chamber is an adjustablechamber diameter.

5. In a coffee maker appliance of unitary form for brewing a variablequantity of coffee, variable-by feed of a variable number of chosenunits of volume of water from a heating chamber to an infusion chamber,the combination comprising a base supporting a column, said base andcolumn being in communication and enclosing the heating chamber, saidcolumn enclosing a water filter chamber, and the top of said columnbeing closable to seal said column, filter and heating chamber 'to apressure-tight condition, a discharge tube communicating with saidheating chamber at a low point therein, the entry to said tube beingcontrolled by a thermally responsive valve sharply responsive to apredetermined temperature, a top for said coffee maker comprising asupport on said column, carrying a coffee infusion chamber removabletherefrom, said coffee infusion chamber being a closed receptacle withan ingress orifice for water from said heating chamber and a dischargeorifice, said infusion chamber being of variable diameter to permitvariable rates of discharge from said chamber through constant depth ofcoffee grounds, and heating means in the heating chamber in heatexchange relation with water therein, said heating means beingselectively controllable at different levels of intensity.

1. A coffee maker comprising in combination, a base, a water heatingvessel on said base having an inlet and an outlet, means for heatingwater in said vessel, means on one portion of the vessel to support acoffee receiver, a column extending upwardly from another portion of thevessel, a coffee infusion chamber supported by the column, means forclosing the inlet, a passage through which heated water may be withdrawnfrom the outlet of the vessel and passed to said infusion chamberthrough an entrance thereto, a water spreader means disposed across theentrance to said infusion chamber, a thermally responsive valve meanscontrolling said passage for said heated water, said valve means beingclosed when the water is below a preset temperature and being sharplyresponsive when the water exceeds said preset temperature to open saidvalve means and permit water under pressure built up in said vessel byheating of the water therein to pass via said passage to said infusionchamber.
 2. A coffee maker comprising a base member, a closable waterheating vessel mounted on the base member, a coffee infusion chamberexterior to the water heating vessel and spaced above the base member;water inlet means for the vessel extending therefrom up to at least thetop of the coffee infusion chamber; a closure element for said waterinlet means; a water flow tube connecting said water heating vessel froma point near the bottom thereof to said coffee infusion chamber; valvemeans controlling the flow in said tube; means responsive to thetemperature in said vessel for operating the valve means, said valvemeans being closed at normal room temperature; means for heating thewater in the vessel to increase the pressure therein when both theclosure element and the valve means are closed; said temperatureresponsive means being effective to open the valve means when the waterexceeds a predetermined temperature, so that the water then flowsrapidly through the valve means and the tube to the coffee infusionchamber.
 3. Coffee making apparatus for heating selective variablequantities of coffeee, comprising a closable pressure-tight waterheating chamber, an infusion chamber, a conduit connecting the heatingchamber and the infusion chamber, a valve controlling water flow throughthe conduit, means responsive to the temperature in the heating chamberfor operating the valve from a closed position when the water therein isbelow a predetermined temperature to an open position when the waterexceeds said temperature, heating means effective when the chamber isclosed to generate pressure in said heating chamber, said pressure beingeffective when the valve is thereafter opened to urge a measuredquantity of heated water from the heating chamber through the infusionchamber, and means to control the flow of heated water through theinfusion chamber in accordance with the quantity of coffee to be brewedin order to maintain a constant infusion time.
 4. Coffee makingapparatus as claimed in claim 3 wherein the means to control the flow ofwater through the infusion chamber is an adjustable chamber diameter. 5.In a coffee maker appliance of unitary form for brewing a variablequantity of coffee, variable by feed of a variable number of chosenunits of volume of water from a heating chamber to an infusion chamber,the combination comprising a base supporting a column, said base andcolumn being in communication and enclosing the heating chamber, saidcolumn enclosing a water filter chamber, and the top of said columnbeing closable to seal said column, filter and heating chamber to apressure-tight condition, a discharge tube communicating with saidheating chamber at a low point therein, the entry to said tube beingcontrolled by a thermally responsive valve sharply responsive to apredetermined temperature, a top for said coffee maker comprising asupport on said column, carrying a coffee infusion chamber removabletherefrom, said cOffee infusion chamber being a closed receptacle withan ingress orifice for water from said heating chamber and a dischargeorifice, said infusion chamber being of variable diameter to permitvariable rates of discharge from said chamber through constant depth ofcoffee grounds, and heating means in the heating chamber in heatexchange relation with water therein, said heating means beingselectively controllable at different levels of intensity.